Quantitative measurement of dislocation density of low carbon steel wire rods and wires

Strain hardening in low carbon steel has been one of the main reasons for unpredictability of tensile strength after cold working. It is therefore important to study the mechanism of strain hardening in steel. This strain hardening can be best described by dislocation density theory. Knowledge of dislocation behavior will make it easier to predict tensile properties of steel after cold working. Study of steel making variables controlling dislocation density and accordingly controlling these variables and achieving desired properties at the customers end is the main purpose of this study.;This research attempts to quantify the dislocation density in steel wire rods, cooled under different Stelmore conditions. These wire rods were further cold drawn to wires to achieve considerable mechanical deformation and dislocation densities were estimated for the same. Quantitative dislocation density measurement enables to correlate mechanical properties such as tensile strength with dislocation densities for wires and wire rods.;Measurement of dislocation density was carried out by using a transmission electron microscope (TEM). TEM microphotographs were studied for dislocation density for each wire and wire rod and quantified using thin foil techniques. Microstructure studies supplement the results.;A detailed literature survey, TEM sample preparation, microphotography and image interpretation, microstructure study, and tensile strength analysis are part of the research work. I studied and explained the interaction between StelmorRTM parameters, tensile strengths, dislocation densities, and amount of cold work done on wire rods with the help of available literature. Steel mills such as Gerdau Ameristeel benefit by gaining better control over tensile strength and increase the quality of products.